"The effect of Mr. Hartwyk's conduct was to deny the Port Authority the opportunity to save money on its legal expenses."

Former Port Authority Deputy General Counsel Christopher Hartwyk, seen her in 2000, pleaded guilty Friday in Manhattan Criminal Court to a charge of "offering a false instrument for filing." Jim Pathe/The Star-Ledger

A former high-ranking lawyer with the Port Authority of New York and New Jersey has admitted he forged a letter in 2009 assuring the bi-state agency that an outside law firm he had hired was providing a 15-percent discount on legal work, the Manhattan District Attorney’s office announced.

The lawyer, former Port Authority Deputy General Counsel Christopher Hartwyk, will serve 20 days of community service after pleading guilty to a single count of offering a false instrument. The Port Authority's headquarters are in Manhattan.

Hartwyk last made headlines in December 2011, when he was forced out of his $215,000 job as the agency's number two lawyer by Gov. Chris Christie. Christie replaced Hartwyk with former state Attorney General Paula Dow, who was awaiting confirmation to a state Superior Court judgeship.

Hartwyk, 53, of South Orange, is a cousin of state Sen. Richard Codey (D-Essex), a bitter foe of the Republican governor. Before Hartwyk was pushed out, Christie had accused Codey of blocking Dow's nomination to the bench in Essex County. Afterward, some of Codey's allies accused Christie of ousting Hartwyk from the Port Authority in retaliation.

Friday's announcement by Manhattan District Attorney Cyrus Vance Jr., said Hartwyk had been instructed by the Port Authority law department to obtain a 15-percent discount from the outside firms it retained. But in the case of one firm, Weil, Gotshal & Manges, Hartwyk failed to obtain the discount, and instead composed a fraudulent letter, addressed to the agency from the firm, with the forged signature of one of the firm's partners.

Weil Goshal, which declined to comment, was not accused of any wrongdoing.

Hartwyk was not accused of trying to enrich himself from the fraud. No motive was given by Vance or others involved in the case, including Port Authority Inspector General Robert Van Etten.

"The effect of Mr. Hartwyk's conduct," Van Etten said in a statement, "was to deny the Port Authority the opportunity to save money on its legal expenses."

Hartwyk's lawyer, Marc Agnifilo, declined to comment on his client's motive, other than to note that Hartwyk was not accused of trying to benefit financially from his actions.

After leaving the Port Authority, Hartwyk joined the firm Genova Burns Giantomasi Webster in March 2012, but left the firm last June. It was not immediately clear what Friday's guilty plea would mean for his ability to practice law.

David Rubin, a past chairman of the New Jersey Bar Association’s Professional Responsibility Committee, said lawyers found to have engaged in professional misconduct face disciplinary measures ranging from a reprimand to disbarment.

He cited Section 8.4(b) of the bar’s Rules of Professional Conduct: “It is professional misconduct for a lawyer to: commit a criminal act that reflects adversely on the lawyer’s honesty, trustworthiness or fitness as a lawyer in other respects.”